How We Test TVs

By
Will Greenwald8 Jan 2019, 2:48 a.m.

Wondering what goes into our HDTV reviews? Here's a look at how we test displays in PC Labs.

Our television reviews are extensive, combining technical laboratory tests with real-world viewing experience. We use testing procedures based on Imaging Science Foundation calibration methodology and standards. The process with which we test TVs is similar to how professional calibrators evaluate home theaters, and is performed by an ISF Level II-certified analyst using some of the most advanced calibration and measurement tools available.

This lets us accurately measure the amount of light a television puts out, how dark it can get while still generating a picture, how accurate its colors are out of the box, and how much input lag it generates.

Equipment

To test televisions, we display test patterns generated by a Murideo SIX-G test pattern generator to send a 4K (and, if the TV is compatible, HDR) signal to the TV, ensuring accuracy and consistency in the video source. After a basic dark room calibration, we measure the light and color output using a Klein K10-A colorimeter, a specialized light meter that can precisely track luminance from 0.0001cd/m2 to 10,000cd/m2 (for comparison, most LCD televisions can't display black levels darker than 0.01cd/m2, and we've seen very few capable of putting out more than 1,000cd/m2 under very specific conditions), and color measurements up to and beyond the BT.2020 color space. We feed data from the meter into SpectraCal's CalMAN 5 software, which we also use to produce our color charts for each review.

Calibration

Most televisions currently available can be tweaked to offer excellent color accuracy if calibrated using ISF procedures and advanced testing equipment. However, we've found that TVs are offering increasingly accurate color levels out of the box—if you use the right settings. Putting your TV into Movie, Cinema, or Calibrated mode and making sure the color temperature is set to the warmest preset (usually labeled Warm) will generally produce the most accurate color out of the box for standard dynamic range content. Additionally, HDR content will usually trigger a TV's built-in HDR modes, providing a different and often more limited selection of picture presets based on the greater amount of information in the signal.

To best measure the average consumer experience, we test TVs based on these settings rather than giving each a full calibration. While we recommend calibration for high-end TVs in complex home theater systems, we also recognize that very few users who spend $800 on a new TV will then spend another $300 on calibrating it.

The Test

We measure black level and peak brightness using a consistent selection of test patterns produced by our signal generator. For LED-backlit TVs, we measure peak brightness based on both full-screen and 18 percent white fields; some TVs are capable of boosting backlight in limited zones, while others lack that capability, so both measurements are noted when considering contrast. OLED TVs can get consistently brighter as less of the screen is fully lit, so we only use an 18 percent white field surrounded by black.

For black level, we use a partial white field and measure based on black parts of the frame. This ensures an accurate black level reading and a realistic contrast measurement, since many TV backlights simply turn off when receiving a signal that's completely black. To calculate contrast ratio, we divide the peak brightness by the black level; for OLED TVs that generate no light in black sections of the screen due to the panel technology, we consider effective contrast to be "infinite."

After we measure peak brightness and black level, we move on to color testing. With the growth of high dynamic range (HDR) and wide color gamut, many TVs can reach beyond the Rec.709 broadcast standard color space. For HDR-compatible TVs, we measure white, red, green, blue, cyan, yellow, and magenta levels in a variety of picture modes, enabling any wide color or HDR setting when available. We compare those results against both Rec.709 and wider DCI-P3 color standards with a D65 white level. For TVs that don't support wide color gamut, we evaluate how close the color measurements come to Rec.709. For TVs that can reach beyond broadcast standards in color, we see whether they can hit DCI-P3 levels. For all color measurements, we consider both range and accuracy, noting if any colors appear skewed or tinted.

Input Lag

With luminance and color measurements recorded, we then measure input lag using a Leo Bodnar Video Signal Input Lag Tester, a small device that plugs into a TV's HDMI port and measures flashes on the screen to determine the amount of time between when the television receives a signal and the screen updates. This isn't affected by refresh rate, since TVs with settings above 60Hz manipulate the signal to produce interstitial frames to make the video look smoother; the vast majority of video signals won't contain more than 60 frames per second.

Motion-enhancing modes that claim 120Hz or higher refresh rates can make games look smoother, but they can also produce a jarring "soap opera" effect when displaying movies and television shows. To get rid of it, see How to Turn Off Motion Smoothing on Your TV.

Viewing Experience

Finally, it's time for some real-world testing. To this end, we watch a variety of content to get a sense of general performance. We have a library of films and documentaries on Blu-ray and Ultra HD Blu-ray to observe how well each TV can handle different types of content, like dark, moody, shadow-filled scenes and bright, colorful nature landscapes.

While streaming media is a consideration, using physical media in our tests ensures that we can get the best idea of what a TV is capable of showing from the highest-quality signal, without any considerations of bandwidth or variable bitrates.

About the Author

Will Greenwald has been covering consumer technology for a decade, and has served on the editorial staffs of CNET.com, Sound & Vision, and Maximum PC. His work and analysis has been seen in GamePro, Tested.com, Geek.com, and several other publications. He currently covers consumer electronics in the PC Labs as the in-house home entertainment expert, reviewing TVs, media hubs, speakers, headphones, and gaming accessories. Will is also an ISF Level II-certified TV calibrator, which ensures the thoroughness and accuracy of all PCMag TV reviews. See Full Bio